Zimbabwe's prime minister has said he won't agree to hold elections in July after President Robert Mugabe said he would go ahead with the long-awaited polls.

The prime minister, Morgan Tsvangirai, said on Wednesday that Mugabe cannot decide on an election date without consent from other leaders in the power-sharing government.

Tsvangirai said any elections held at Mugabe's behest would not be deemed "legitimate".

"It seems they are determined to commit suicide, it is what they want," he said at a press briefing of civic leaders.

Mugabe was forced by regional leaders to form a coalition government with former opposition leader Tsvangirai after violent and disputed elections in 2008.

The nation's highest court in May ordered Mugabe to hold polls by the end of July, arguing that the elections should be linked to the dissolution of the parliament at the end of its current five-year term on 29 June.

Mugabe has said he will abide by the ruling and hold the vote on 31 July despite objections from his partners in the coalition. Tsvangirai has said he wants polls to end the four-year-old coalition in September at the earliest.

A lawsuit was brought to the court on 24 May to force Mugabe to call early polls. The private court application claimed the country could not be run without the existence of the parliament, rendering the government illegal.

A new constitution overwhelmingly accepted in a 16 March referendum requires amendments to voters' lists as well as a 30-day registration of new voters that will end on 9 July.

Tsvangirai claimed the lawsuit was instigated by Mugabe's Zanu-PF party loyalists eager for early polls so that they can take advantage of loopholes in the electoral laws to rig the vote.

"That ruling is a political directive which has been given a legal effect, it doesn't create an environment for a legitimate election," Tsvangirai said.

Mugabe, 89, who has ruled the country since independence from colonial rule in 1980, has been accused of appointing sympathetic judges from the justice ministry and the legal profession.

Tsvangirai's Movement for Democratic Change party is also demanding media reforms to end bias by the nation's dominant state media controlled by Mugabe loyalists and an end to political intimidation by the partisan police and military.

"We want to remove all obstacles to a free and fair election. If Zanu-PF wants to roughshod us, I will just stand up and say I will not agree with you," Tsvangirai said.